My unit also seems to be a little slower page turns after the update (someone else mentioned this earlier). Also, when turning on/off wifi from within a book, there is a very long pause when returning to the book using the back button. Not a huge deal, but it is quite noticeable.

My experience is quite different. There is no reduced speed with page turns post-update. The rate is still very fast. There is also no slowdown whatsoever returning to a book after selecting wireless -- it is nearly instantaneous.